In the state of the art apparatus which consist, for example, of a microwave waveguide which is connected via a coupling point to a funnel or horn antenna, are known. By means of this antenna the microwaves are coupled into a vacuum coating chamber through a quartz glass window, making a plasma CVD process, for example, possible in this chamber.
Furthermore, apparatus are known which have a microwave waveguide which by means of a coupling point transmit the microwaves to a microwave waveguide resonator.
This waveguide resonator is characterized by a standing interference pattern of the microwave field, as well as one or more coupling points for supplying the glow discharge for anticorrosion processes and ECR wafer dry etching processes.
These known apparatus with funnel or horn antennas have the disadvantage that, among other things, the quartz glass window between the antenna and the vacuum chamber is also coated during the coating process and thus affects or prevents the passage of the microwaves.
The apparatus with a microwave waveguide resonator have the disadvantage that tuning of the resonator length, resonator position and the coupler is necessary. Moreover, due to the standing interference pattern of the microwave field, in many cases a plasma that is not sufficiently uniform spatially is obtained, and consequently an unsatisfactory distribution of the coating rates, in a PCVD process, for example.
It is therefore the object of the present invention, first to find an apparatus that is independent of a device, such as the quartz glass window for example, which will lastingly affect the microwaves before they enter into the interior of a coating chamber. Secondly, an apparatus is to be found which, over the average time, will permit a spatially more uniform distribution of the coating rates of large-area substrates, such as searchlight reflector inserts, in a PCVD process.